SnapdragonCamera: Fix ANR after capturing pictures continuously

When finish once capture picture, camera need get available space
of SDCard/Internal storage and update available number to UI. It is
a I/O operation and may block a few millisecond. Currently camera
get available space in UI-Thread. So capturing pictures continuously
may cause ANR, though it is happened rarely.
By moving this operation to non-UI thread, can solve this issue.

Change-Id: I397e07117f88e56cbe2ad0b893e2bad8b3075ab5
CRs-Fixed: 1022382
2 files changed